1. Field of the Invention
The present invention relates to an interchangeable lens which is selectively mountable to a packing-compatible camera body and a packing-incompatible camera body, and also relates to a camera system which includes a packing-compatible camera body, this packing-incompatible camera body and a interchangeable lens.
2. Description of the Related Art
Conventionally, in order to provide a water-resistant camera system which is composed of at least one interchangeable lens and a camera body, the interchangeable lens is provided at the rear end thereof with an annular packing made of a resilient material. This annular packing comes into elastic contact with a body-side mount (body mount) of a camera body when the interchangeable lens is mounted to the camera body.
Camera manufacturers manufacture their own-brand camera bodies so that all these camera bodies have body-side mounts of the same shape and size to make all their own-brand interchangeable lenses compatible with all their own-brand camera bodies (note that the shape and size of the body-side mount differ according to camera manufacturers).
However, since camera manufactures unify the shapes of the body-side mounts of their own-brand camera bodies as just described, the user who has bought a packing-incorporated interchangeable lens is inconvenienced, which will be hereinafter discussed with reference to FIGS. 8 and 9.
FIG. 8 shows a state where an interchangeable lens 010 provided with an annular packing 015 made of a resilient material is mounted to a camera body 020A and are both produced by the same camera manufacturer, and FIG. 9 shows a state where the same interchangeable lens 010 is mounted to another type of camera body 020B produced by the same camera manufacturer.
The interchangeable lens 010 shown in FIG. 8 and the interchangeable lens 010 shown in FIG. 9 are the same. The interchangeable lens 010 is provided at the rear end thereof with a lens-side mount ring (lens mount) 012, and the annular packing 015 is fixed to an outer peripheral surface of the lens-side mount ring 012. The rear end of the annular packing 015 in a free state projects rearward from front outer flange of the lens-side mount ring 012.
The camera body 020A, a part of which is shown in FIG. 8, is designed as a packing-compatible camera body which is compatible with the interchangeable lens 010. Upon the lens-side mount ring 012 of the interchangeable lens 010 being coupled to a body-side mount ring (body-side mount) 022 of the packing-compatible camera body 020A, the rear end of the annular packing 015 comes into elastic contact with the front surface (packing contacting surface) of an outward flange portion 024 of the body-side mount ring 022 (which is formed at the front end thereof) while being resiliently deformed. Therefore, in the case shown in FIG. 8, the joint between the interchangeable lens 010 and the packing-compatible camera body 020A is made watertight by the annular packing 015.
The camera body 020B, a part of which is shown in FIG. 9, is designed as a packing-incompatible camera body. Although the packing-incompatible camera body 020B is designed without consideration of connectability (compatibility) with the interchangeable lens 010, it is possible that the lens-side mount ring 012 of the interchangeable lens 010 be coupled to the body-side mount ring 022 of the packing-incompatible camera body 020B as shown in FIG. 9 because the body-side mount ring 022 of the packing-incompatible camera body 020B is identical in shape and size to the body-side mount ring 022 of the packing-compatible camera body 020A. Upon the interchangeable lens 010 being mounted to the packing-incompatible camera body 020B, the rear end of the annular packing 015 comes into elastic contact with the front surface (packing contacting surface) of the outward flange portion 024 of the body-side mount ring 022 while being resiliently deformed.
In addition, Japanese Unexamined Patent Publication H11-174562 is also related art with respect to the present invention.
A ring-shaped biasing member R1′ including a pair of resilient projections R1a′ is fixed to a rear end surface of the body-side mount ring 022 of the packing-compatible camera body 020A. On the other hand, a ring-shaped biasing member R2′ (including a pair of resilient projections R2a′) which is identical in shape and size to the ring-shaped biasing member R1′ is fixed to a rear end surface of the body-side mount ring 022 of the packing-incompatible camera body 020B. Upon the lens-side mount ring 012 of the interchangeable lens 010 being coupled to the body-side mount ring 022 of either of the two camera bodies 020A and 020B, the pair of corresponding resilient projections R1a′ or R2a′ presses the lens-side mount ring 012 rearward to remove play between the lens-side mount ring 012 and the body-side mount ring 022 in the optical axis direction (horizontal direction with respect to FIGS. 8 and 9).
The biasing force of the pair of resilient projections R1a′ of the ring-shaped biasing member R1′ of the packing-compatible camera body 020A is predetermined in consideration of the elastic force which is exerted on the body-side mount ring 022 of the packing-compatible camera body 020A by the annular packing 015 (i.e., the biasing force of the annular packing 015 for biasing the interchangeable lens 010 forward with respect to the body-side mount ring 022). Therefore, upon the interchangeable lens 010 being mounted to the packing-compatible camera body 020A, the position of the interchangeable lens 010 relative to the packing-compatible camera body 020A in the optical axis direction is finely adjusted by a resultant of the following two forces: the forward biasing force of the annular packing 015 and the rearward biasing force of the pair of resilient projections R1a′ so that the interchangeable lens 010 is held at an appropriate position relative to the packing-compatible camera body 020A in the optical axis direction.
On the other hand, since the packing-incompatible camera body 020B is designed without consideration of the annular packing 015 coming in elastic contact with a front surface of the outward flange portion 024 of the body-side mount ring 022, the biasing force of the pair of resilient projections R2a′ of the ring-shaped biasing member R2′ is predetermined without consideration of the elastic force which is exerted on the body-side mount ring 022 of the packing-compatible camera body 020B by the annular packing 015 (i.e., the biasing force of the annular packing 015 for biasing the interchangeable lens 010 forward with respect to the body-side mount ring 022).
Therefore, if the annular packing 015 comes in elastic contact with the body-side mount ring 022 when the interchangeable lens 010 is mounted to the packing-incompatible camera body 020B as shown in FIG. 9, not only the biasing force of the pair of resilient projections R2a′ of the ring-shaped biasing member R2′ but also the biasing force of the annular packing 015 are exerted on the body-side mount ring 022 and the lens-side mount ring 012, which causes the position of the interchangeable lens 010 relative to the packing-incompatible camera body 020B in the optical axis direction to deviate from an intended proper position. Consequently, the optical performance of the interchangeable lens 010 deteriorates.
Therefore, in the case where the user buys the new interchangeable lens 010 that is provided with the annular packing 015, although the new interchangeable lens 010 can be mounted to the packing-compatible camera body 020A and achieve a lens optical performance in accordance with the lens design thereof, if the new interchangeable lens 010 is mounted to the packing-incompatible camera body 020B, which may be already owned by the user, a lens optical performance cannot be achieved in accordance with the lens design thereof.